Inhibition mechanism of nitrogen on ignition and combustion of AlH3 via ReaxFF MD simulation and reaction kinetic study

GL Li and HP Jiang and JP Liu and W Gao, CHEMICAL ENGINEERING JOURNAL, 522, 167584 (2025).

DOI: 10.1016/j.cej.2025.167584

Safe production and widespread application of aluminum hydride (AlH3) are limited by unstable hydrogen evolution and explosion risk. To address the critical safety concern, the influence of chemical bonding effect, atomic diffusion behavior, as well as the thermodynamic and structural property of AlH3-nanoparticle (AHNP) under varying N-2/O-2 atmospheres during the ignition and combustion periods are studied by reactive molecular dynamics methods. The explosion suppression mechanism of N-2 on AlH3 is also clarified by kinetics modeling. Results reveal that N-2 is pivotal for the inhibition of the ignition and combustion of AlH3 nanoparticle, as it hinders the bonding effect of aluminum (Al) atoms in alumina (Al2O3) shell and O atoms in ambient environment, Al atoms in core-AlH3 and oxygen atoms in Al2O3 shell (sO), and the development of an Al-rich environment on shell inner surface. Fracture of Al2O3 shell is observed in AHNP combustion, and the moment in pure-N-2 system is delayed by 221 % compared to that of 90 %N-2, which is mainly influenced by combustion temperature. AlH3-nanoparticle combustion can be divided into four distinct phases: surface combustion, hydrogen combustion, slow combustion and self-sustaining combustion. Hydrogen combustion is obviously observed in 0 % similar to 50 % N-2 systems, and sO atoms are the essential oxidants for the self-sustaining combustion of AHNP in pure-N-2 system. Temperature rise rate of surface combustion and average combustion temperature for pure-N-2 system decrease by 85.2 % and 49.8 % compared to pure-O-2. An increase in N-2 concentration directly reduces O-2 content to inhibit AlO radicals generated by Al + O-2 < = > AlO + H-2, and further suppresses the reactions of AlOAlO + O < = > Al2O3 and AlOAlO < = > 2AlO, thereby inhibiting the transition of AlH3 to Al2O3.

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